In the past, for the purpose of installing load-bearing concrete piles in situ, it has been regular practice in the trade to rotate a hollow shafted, spiral-flighted auger into an earth situs to predetermined depth and then to inject fluid cement mortar through the auger shaft while withdrawing the auger, thereby to fill the drilled cavity, after which the cement mortar was allowed to harden as a solid pile column within the drilled cavity. Such prior methods, however, required use of a substantial amount of heavy, pile drilling equipment for handling large augers, and for pumping cement mortar into the augered cavities in the situs. A major problem with use of the prior pile forming methods in general resided in the fact that each pile cavity of a plurality thereof had to be separately drilled in the situs with use of a continuous flight auger, through which fluid cementitious material was pumped into each respective cavity with progressive withdrawal of the auger. Consequently, the usual cement supply trucks were often required to stand idle while the cavities were being drilled, and quite often the drilling work was seriously hampered by delays in arrival of such supply trucks.